This invention relates to solenoid operated fuel injectors that are used in fuel injection systems of internal combustion engines and, in particular, to fuel injectors having two independent subassemblies.
It is known in the art relating to fuel injectors for internal combustion engines to assemble a valve group subassembly and a power group subassembly, which are then assembled together. After final assembly, the coil associated with the power group subassembly, and now part of the injector, is energized and used to calibrate the assembled injector. Such an injector assembly is limited to a specific power group subassembly because that power group subassembly was used to calibrate the injector.
The present invention provides a solenoid actuated fuel injector that is not limited to use with a specific power group subassembly. More specifically, the injector of the present invention is comprised of an independently operational and calibrated hydraulic metering subassembly and an independent power group subassembly, making it possible to use the hydraulic metering assembly with any of a variety of power group subassemblies.
As hereinafter more fully described, a master coil associated with a test unit is used to calibrate the fuel metering subassembly instead of calibrating the injector using its own coil or power group subassembly. As such, the power group subassembly can be added at a later time to the hydraulic metering subassembly to make a complete working injector. Therefore, by having two independent subassemblies, costly production operations are eliminated, particularly in the area of tooling and changeovers for electrical connector variations.
A method of making the solenoid actuated fuel injector includes assembling a hydraulic metering subassembly having an armature/needle assembly movable between open and closed positions to meter the discharge of fuel from the injector. The hydraulic metering subassembly is calibrated with a master coil associated with a test unit. Then, the power group subassembly having an actuating coil and a magnetic flux return path is assembled. Finally, the two subassemblies are mechanically connected together such that a magnetic circuit is completed between the subassemblies to operate the armature/needle assembly between open and closed positions upon energizing and deenergizing of the coil.
As stated, the fuel injector of the present invention includes a hydraulic metering subassembly and a power group subassembly. The hydraulic metering subassembly has an elongated ferromagnetic inlet tube for conveying fuel from a fuel inlet to a fuel outlet. A valve body shell is connected to an end of the inlet tube and encloses an upper end of a valve body assembly having an armature/needle assembly. Fuel is prevented from or allowed to discharge from the injector by moving the armature/valve assembly between valve closed and open positions. The inlet tube, valve body and valve body assembly are welded together to form a completely sealed hydraulic metering subassembly.
The power group subassembly has a coil assembly housing including a magnetic flux return path. The housing encloses a coil assembly, which generates electromagnetic forces to move the armature/needle assembly between the valve closed and open positions. The power group subassembly may comprise different shapes or types of coil assemblies depending on the particular fuel rail with which the injector is to be used, since the hydraulic metering subassembly is completely separate from the power group subassembly. However, the injector is completed when the power group subassembly is secured to the hydraulic metering subassembly so that a magnetic circuit is completed between them to operate the fuel injector.
These and other features and advantages of the invention will be more fully understood from the following detailed description of the invention taken together with the accompanying drawings.